Specifically, bytes (always, from what I could find) had this error message:
>>> b'' + ''
TypeError: can't concat bytes to str
while str, after a change in issue26057, was made to:
>>> '' + b''
TypeError: must be str, not bytes
from the previous form of "TypeError: Can't convert 'bytes' object to str implicitly".
I think these could be changed to conform with what the other sequences generate and fall in line with the error messages produced for other operations.
Specifically changing them to:
>>> b'' + ''
TypeError: can only concatenate bytes (not 'str') to bytes
and similarly for str.
If this idea makes sense, I can attach a patch that addresses it.